Various communication systems communicate using multiple transmit and/or receive antennas. Such communication schemes are referred to as Multiple-Input Multiple-Output (MIMO) schemes. MIMO configurations are used, for example, in Evolved Universal Terrestrial Radio Access (E-UTRA), also referred to as Lone Term Evolution (LTE), and LTE-Advanced (LTE-A) systems. MIMO communication typically involves feeding back communication channel information from the receiver to the transmitter.
Some MIMO feedback schemes use precoding codebooks, i.e., predefined sets of precoding matrices that are agreed upon between the transmitter and the receiver. The use of codebooks enables the receiver to report its estimated channel or request a preferable precoding scheme with small signaling overhead. Codebook-based feedback schemes are described, for example, in 3GPP Technical Specification 36.213, entitled “Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Layer Procedures (Release 8),” (3GPP TS 36.213), version 8.6.0, March, 2009, which is incorporated herein by reference.
The description above is presented as a general overview of related art in this field and should not be construed as an admission that any of the information it contains constitutes prior art against the present patent application.